From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755941AbaAHJkm (ORCPT ); Wed, 8 Jan 2014 04:40:42 -0500 Received: from cantor2.suse.de ([195.135.220.15]:49681 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754162AbaAHJki (ORCPT ); Wed, 8 Jan 2014 04:40:38 -0500 Date: Wed, 8 Jan 2014 10:40:36 +0100 From: Michal Hocko To: linux-kernel@vger.kernel.org, Mel Gorman , Andrew Morton , linux-mm@kvack.org, Dave Hansen , David Rientjes Subject: Re: [RFC] mm: prevent set a value less than 0 to min_free_kbytes Message-ID: <20140108094036.GA27937@dhcp22.suse.cz> References: <20140108084242.GA10485@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140108084242.GA10485@localhost.localdomain> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 08-01-14 16:42:42, Han Pingtian wrote: > If echo -1 > /proc/vm/sys/min_free_kbytes, the system will hang. > Changing proc_dointvec() to proc_dointvec_minmax() in the > min_free_kbytes_sysctl_handler() can prevent this to happen. You can still do echo $BIG_VALUE > /proc/vm/sys/min_free_kbytes and make your machine unusable but I agree that proc_dointvec_minmax is more suitable here as we already have: .proc_handler = min_free_kbytes_sysctl_handler, .extra1 = &zero, It used to work properly but then 6fce56ec91b5 (sysctl: Remove references to ctl_name and strategy from the generic sysctl table) has removed sysctl_intvec strategy and so extra1 is ignored. > Signed-off-by: Han Pingtian That being said I do not think this will fix any real world problem but just for sake of correctness After changelog is updated feel free to add my Acked-by: Michal Hocko > --- > mm/page_alloc.c | 7 ++++++- > 1 files changed, 6 insertions(+), 1 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 77937e0..a9dcfd8 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5692,7 +5692,12 @@ module_init(init_per_zone_wmark_min) > int min_free_kbytes_sysctl_handler(ctl_table *table, int write, > void __user *buffer, size_t *length, loff_t *ppos) > { > - proc_dointvec(table, write, buffer, length, ppos); > + int rc; > + > + rc = proc_dointvec_minmax(table, write, buffer, length, ppos); > + if (rc) > + return rc; > + > if (write) { > user_min_free_kbytes = min_free_kbytes; > setup_per_zone_wmarks(); > -- > 1.7.7.6 > -- Michal Hocko SUSE Labs